As the title explains, I am looking to generate a series of random short values. Because there is no Random.nextShort() function, the easiest way to do what I want seems to be to cast integers to short, using:
Random rand = new Random(int seed);
(short) rand.nextInt()
However, I don't fully understand how this casting takes place, and so I cannot be sure that the resulting short values would still be random. Is this the case? Thanks in advance.
A short cast of an int works by bitwise truncation. As long as the integers are randomly distributed, the short values should be also - yes.
From the Java Language Specification 5.1.3:
A narrowing conversion of a signed integer to an integral type T simply discards all but the n lowest order bits, where n is the number of bits used to represent type T.
int has 32 bits, short has 16. Essentially the conversion is the same as adding (or subtracting) 65536 (which is 2 to the power of 16) until the value is in the range representable by short. Thus, there are exactly 65536 int values which map to each possible short value.
The canonical way is to do short result = (short)(rand.nextInt(Short.MAX_VALUE-Short.MIN_VALUE+1) + Short.MIN_VALUE). The reason for this is that you want a number from a range that spans Short.MAX_VALUE-Short.MIN_VALUE+1 values, and starts at Short.MIN_VALUE.
Simple truncation may be enough fort short (and if speed matters to you, it's probably also faster), but this approach works for any range.
Let's say you want a random number between -5 and 12 (both inclusive), you will then call rand.nextInt(12-(-5)+1)+(-5), or if you simplify all the calculations: rand.nextInt(18)-5.
A good solution to avoid error is :
Random rand = new Random(int seed);
short s = (short) rand.nextInt(Short.MAX_VALUE + 1);
If you also need negative short :
short s = (short) rand.nextInt(Short.MAX_VALUE - Short.MIN_VALUE + 1) + Short.MIN_VALUE;
A fastest solution :
short s = (short) random.nextInt(1 << 16); // any short
short s = (short) random.nextInt(1 << 15); // any non-negative short
The number will be still random, but you can have problem with different max/min values of this number, for more info, look at first answer here here
I think this will not work because an int is a lot bigger than a short.
Just take a random float or double (the values are between [-1;1]) and multiply them by the max value of a short:
short i= (short) rand.nextFloat() * Short.MAX_VALUE;
